Articulations and Body Movements

Study Notes

An articulation is a joint.
Articulations are classified either structurally or functionally.
Structurally joints are classified as fibrous, cartilaginous or synovial joints.
Functionally joints are classified as synarthroses, amphiarthroses or diarthroses.
Synarthroses are non-movable joints.
Amphiarthroses are slightly movable joints.
Diarthroses are freely movable joints.

Fibrous joints consist of bones held together by fibrous tissues.
Most fibrous joints are synarthrotic or non-movable.
Fibrous joints have no joint cavity.
Types of fibrous joints are sutures, syndesmoses, and gomphoses.
Sutures are joints with bones with irregular edges interlocked by short connective tissue fibers.
Syndesmoses are joints with bones connected by short ligaments.
A Gomphosis is a joint that holds the teeth in the mandible via the periodontal ligament.

Cartilaginous joints have articulating bones connected by plates or pads of cartilage.
Cartilaginous joints have no joint cavity.
Most cartilaginous joints are amphiarthrotic (slightly movable).
Types of cartilaginous joints are symphyses and synchondroses.
Symphyses are joints which have bones that are connected by a broad flat disc of fibrocartilage.
Synchondroses are bones connected by hyaline cartilage.

Synovial joints have bones separated by joint cavities filled with synovial fluid.
Synovial joints are diarthrotic or freely movable.
Characteristics of synovial joints:
- Articular Capsule: 2 layers - a fibrous capsule of dense irregular connective tissue and a layer of synovial membrane which secretes synovial fluid.
- Articular cartilage (hyaline) on the surfaces of the articulating bones.
- Ligaments (hold bones of joint together).
- Bursae (fluid filled sacs).
- Articular discs may be found (Meniscus), (padding between articulating bones).
Types of synovial joints: plane or gliding, hinge, pivot, condyloid/ ellipsoidal, saddle, ball and socket.

The Origin is the point of attachment of muscle that is immobile.
The Insertion is the point of attachment of muscle that moves.
A Contraction of muscle causes the insertion to move towards the origin.
Flexion decreases the angle between the origin and the insertion.
Extension increases the angle between the origin and the insertion.
Abduction is a movement away from the midline.
Adduction is a movement towards the midline.
Rotation is a movement around the long axis of a bone.
Circumduction is a movement that makes an imaginary cone along the long axis of a bone.